Question

A 200 mL flask contains 2.00 grams of O2 and 2.00 grams of He at 25 degrees celsius. What is the total pressure? What is the pressure of the He?

Answer 1

PV= nRT

P = Pressure in atm

V= Volume in Liter

n = no of moles

R = 0.0821 L atm K-1 Mol-1

T = Temperature in Kelvin

Using the equation we can calculate the moles of He and O2

Moles of He

P = ? V = 0.2 Liter n = 2 /2 = 1 Moles T = 273 + 25 = 298 K

P = nRT / V = 1 x 0.0821 x 298 / 0.2 = 122.329 atm  

the pressure of the He = 122.329 atm

Moles of O2

P = ? V = 0.2 Liter n = 2 / 32 = 0.0625 Moles T = 273 + 25 = 298 K

P = nRT / V = 0.0625 x 0.0821 x 298 / 0.2 = 1.529 atm  

Total pressure = 122.329 atm + 1.529 atm = 123.85 atm